1. Field of the Invention
The present invention relates to an improved method and apparatus for calibrating the apex offset on fiberoptic connector measuring interferometer and more particularly pertains to calibrating the apex offset on a fiberoptic connector measuring interferometer, the calibrating being done in an accurate, rapid, simple and economical manner.
2. Description of the Prior Art
Fiberoptic connectors are used around the world to construct networks that enable extremely fast, high bandwidth and reliable data communications. These connectors are an integral part of the network technology that enables the present day internet, cellular voice/data and phone service. Singlemode optical fibers, primarily used to carry this information efficiently, have extremely strict physical and optical parameters, since the portion of the fiber (fiber core) that actually carries the laser light is typically just 7-9 microns in diameter. At key points in the network fiberoptic connectors are used to attach transceivers, hubs, switches, amplifiers and a myriad of other optical components required to create the complete optical network. With such small diameters involved, it is clear that the physical parameters of the endface geometry are extremely strict to ensure intermatability of these connectors—at a common level of performance, from numerous vendors.
To ensure physical contact of the optical fibers, not only must they be aligned laterally to ensure the fiber cores mate with minimal (sub-micron) offset, minimizing insertion loss—but they must also mate in physical contact with each other to avoid changes in the index of refraction (such as an air gap), that can lead to a detrimental phenomenon known as back reflection. Both back reflection and insertion loss significantly detriment network performance and must be avoided at all cost. Strict manufacturing tolerances in both the ferrule and fiber are used to insure core alignment and thus minimal loss. To prevent back reflection that can destabilize the lasers generating the light transmitted in the fiber cores, physical contact (or angled physical contact) must be assured between the fibers of two mating connectors. This can be achieved by spherically polishing (or angled spherically polishing) the connector endfaces to a specific radius—and ensuring that the fiber does not protrude or become undercut, with respect to the ferrule surface, by more than approximately 100 nanometers. The apex is defined as the highest point on spherically polished ferrule, and ideally is coincident with the center of the fiber. Any deviation from the ideal is known as an apex offset. Typically, apex offset is expected to be less than just 50 microns. With expected geometry parameters of just a few microns or nanometers required to ensure optimal performance of the connectors, it becomes clear that measuring these parameters with sufficient accuracy and repeatability can be challenging.
Due to their inherent accuracy, interferometers have been the defacto standard for measuring the critical endface geometry parameters (Radius of curvature, Fiber Height, Apex Offset, Angle, Surface Roughness etc.) of fiber optic connectors after polishing, for over 20 years. To measure these parameters accurately—in particular the apex offset, it is essential that the fixture holding the connector during measurement be very accurately aligned with the interferometers optical axis or reference mirror. Small residual errors can be quantified and compensated for in software. Larger errors can be compensated for by physically realigning the fixture, the interferometers optical axis (or the interferometer itself) relative to each other. Either way, the resulting calibration will insure that the apex of a PC (Physical Contact) fiberoptic connector or the key error and angle of an APC (Angled Physical Contact) connector are measured accurately.
To achieve the correct calibration of the apex offset on a fiberoptic connector measuring interferometer, it is typically necessary to either rotate the connector multiple times—and fit a circle to the various apex offsets—or mechanically key a calibration connector, in a fixed rotational orientation—such that the magnitude and direction (bearing) of the calibration connectors apex offset is known, with respect to its “keyed” rotational orientation.
The multiple measurements at different points of rotation (typically 45-60 degrees) method is very accurate, requires no prior knowledge about the connector's apex offset or direction (bearing), and can provide additional information regarding the quality of the fixturing—however, it takes much longer than a single measurement.
The single measurement method is faster, however, it also requires physical input from the operator to provide the unique previously characterized magnitude and direction (bearing) information of the endface, relative to the keyed (known) mechanical rotational orientation. Any mistake or error in this inputted information would result in incorrect calibration and thus incorrect measurements—until the next “correct” calibration was performed. This could potentially result in a vendor shipping non-compliant products to a customer.
The use of methods and apparatuses for calibrating the apex offset on a fiberoptic connector measuring interferometer is known in the prior art. More specifically, methods and apparatuses for calibrating the apex offset on fiberoptic connector measuring interferometers of known designs and configurations previously devised and utilized are known to consist basically of familiar, expected, and obvious structural configurations, notwithstanding the myriad of designs encompassed by the crowded prior art which has been developed for the fulfillment of countless objectives and requirements.
While these devices fulfill their respective, particular objectives and requirements, they do not describe an improved method and apparatus for calibrating the apex offset on fiberoptic connector measuring interferometer that allows for calibrating the apex offset on a fiberoptic connector measuring interferometer, the calibrating being done in an accurate, rapid, simple and economical manner.
In this respect, the improved method and apparatus for calibrating the apex offset on fiberoptic connector measuring interferometer according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides an apparatus primarily developed for the purpose of calibrating the apex offset on a fiberoptic connector measuring interferometer, the calibrating being done in an accurate, rapid, simple and economical manner.
Therefore, it can be appreciated that there exists a continuing need for a new and improved method and apparatus for calibrating the apex offset on fiberoptic connector measuring interferometer which can be used for calibrating the apex offset on a fiberoptic connector measuring interferometer, the calibrating being done in an accurate, rapid, simple and economical manner. In this regard, the present invention substantially fulfills this need.